In manufacturing of a semiconductor device such as an ultra-high speed bipolar or an ultra-high speed CMOS, an epitaxial growth technique for a single crystal, the impurity concentration and film thickness of which are controlled, is an inevitable to improve the performance of the semiconductor device. As an epitaxial growth method to generate a thin single crystal film on a wafer, an atmospheric pressure chemical vapor phase growth method is generally used. Depending on the cases, a low-pressure chemical vapor deposition (LPCVD) method is used. A wafer is put in a chamber, an atmospheric pressure (0.1 Mpa (760 Torr)) or a vacuum atmosphere having a predetermined degree of vacuum is kept in the chamber, and a process gas obtained by mixing a silicon source with a dopant such as a boron compound, a phosphorous compound, or an arsenic compound is supplied into the chamber while keeping the wafer heated and rotated. On a surface of the heated wafer, a thermal decomposition reaction or a hydrogen reduction reaction is performed to generate a single crystal thin film doped with boron (B), phosphorous (P), or arsenic (As).
For example, in order to manufacture a semiconductor device such as an IGBT (insulating gate bipolar transistor), an epitaxial growth technique which generates a thick and uniform high-quality single crystal film is required. For example, in a conventional MOS device or the like, only a film thickness of several μm or less is necessary. However, in an IGBT or the like, a film thickness of several micro-meters to one hundred and several tens of micro-meters is necessary. For this reason, the wafer is rotated at a high speed to always supply a new gas onto the wafer surface, so that a growth rate of a crystal film is improved. Furthermore, the wafer is uniformly heated to improve the in-plane uniformity of the thickness of the film to be formed.
FIG. 7 is a conceptual diagram showing a conventional vapor phase growth apparatus in which a plurality of heaters are arranged to uniformly heat a wafer. FIG. 8 is an explanatory diagram of a problem of the conventional vapor phase growth apparatus shown in FIG. 7. FIG. 8 shows a manner by which a wafer 302 is heated while controlling an internal heater 305 and an external heater 306 on the basis of temperature information measured by a temperature measuring unit 308 shown in FIG. 7. When the wafer 302 is heated by using both the internal heater 305 and the external heater 306, a central portion of the wafer 302 is heated by receiving radiation heat from the internal heater 305. The edge portion of the wafer 302 is heated by giving conductive heat through the susceptor 303 heated by the external heater 306. At this time, a high-temperature region which is overheated to a temperature higher than those of the central portion and the edge portion of the wafer 302 is generated in the plane of the wafer 302 (singular point of temperature) under the influence of both the radiation heat from the internal heater 305 and the conductive heat supplied from the external heater 306 through the susceptor 303. As a result, the thickness of a crystal film generated around the singular point of temperature of the wafer 302 becomes abnormal.
When a vapor phase growth reaction is to be executed, the wafer 302 is placed such that the edge portion of the wafer 302 is in contact with the susceptor 303. In this case, since heat is easily transmitted from the edge portion of the wafer 302 to the susceptor 303 and let out of the susceptor 303, the temperature of the wafer edge portion decreases, and the in-plane temperature distribution of the wafer is not uniform. In order to cope with this, as shown in FIGS. 7 and 8, a plurality of heaters are arranged to supplementary heat the edge portion of the wafer 302 and to suppress a decrease in temperature of the edge portion of the wafer 302. However, due to the countermeasure, according to the above description, a state in which a singular point of temperature is generated in another region in plane of the wafer 302 is disadvantageously caused.
In this case, even though a power of any one of the internal heater 305 and the external heater 306 or power of both of them are controlled to try to correct the ununiformity of the in-plane temperature distribution of the wafer 302, it is difficult to completely eliminate a singular point of the temperature distribution. As a result, the temperature distribution in the entire surface of the wafer 302 cannot be made uniform, and formation of a crystal film having a uniform thickness cannot be realized. Furthermore, when the in-plane temperature distribution of the wafer 302 is not uniform in a vapor phase growth reaction, a crystal defect occurs in the crystal film to be formed, and a wafer having quality enough to be used to manufacture a high-performance semiconductor device cannot also be produced (see JP-A 2001-345271(KOKOAI)).